Electrical measuring instrument.



WITNESSES L. W. CHUBB.

ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED FEB. 7. 1915.

Paten td J an. .15, 1918.

Snob/uneasy 1 O'f'l ven from the line 2a 25 30x ea 55 Cycies mvEwTok Lews W; Cm u b b.

/ ATTORNEY qnency.

UNITED STATES,

LEWIS w. mom; or rrrrsnonelgrnnnsypvwfi ngerenegfroiwge'rinmf ELECTRICAND MAnUFAc'ronmeeoMrnNY, A QRQBQMTIQHIOE: PENNSV To all whomz't mayconcern: p v Be it known that I, LEWIS W. Cnomi, 2y citizen of theUnited St'etes,.end a resident of Pittsbur l1, in the count of Alleghenyand State 0 Pennsylvania, ll new a! d useful Improvenmnt in Electrical.Measuring Instruments, of whichthe fo1- lowing is a specification. 1 j;2

My lnvention relates to eleetr'iealmeasuring mstruments and,particularly to instruments for indicating therrest or maximum values ofvoltage waves having any fre- The object of my invention is to providemeans for correetlng the indicatlons of a crest voltmeter in accordancewith thelreqnency of the voltage to bra-measured;

U. svapplication, Serial No. 798,529, filed 0etober 31, 1913,;by Q. L.Fortescue and a'ssi nod to the -Westinghonse Electric end .anufacturingGompnny; discloses amethod of measuring the maxlmum or crestjvnlu-e-ofthe voltage lmpressed on agcmmt lwlncheonsists in measuring. thecharging" current of a condenser that 13 connected across the/01rtheinstrument in accordance with theflfre quency. Of course, theI'GSlSlQO]? shon lcl used, it

adjusted-{ or each change in frequency,-

The .single figure of the accompanying drawing is e. cllagre rxim nticview of [app mtus embodying my invention; ,l"

One terminal 2 of the primary wintlinga transformer i is connected to a'gTOUIIQ? ed casing l, and 1ts otherternnnal-fi 1315011 neeted toaternnneleonglueto-r (i Theta mine conductor 6 is snrroumled bynlter natelayers of ineulating material 7 and em foil 8 to constitute a condenserterminal bushing 9 of a definite capacitance. The outer layer 8 oftin-foil is bonnected through u v Applieetion and Febrizery:'i ,-1916lSerlfilfi105 15k and al indlca'ting'finstrnlnen ave in'ventedn theclrcuitill. orthe'purposefof jsl which may be: connected between t T20an'cl 21=ofthe circuit 12; TheTesi sto'r' [trans orrner', thecliargin'g' turrent' -circ'uit ieonnecteol 'in ishiin't. rene resistorl0. 1 -The value -"OFFICE.

new

' circuit 12 eonxprising a reel to n: direct-current amineter; 'is shuntrelatiohmtp the re'sletm f" contact-making "and breaking (let 1cconnected between "the points I7" we is divided into three sectionsf23;on "and iepToV/ided with seneee I able contaet member'QS; Anyucls edtion of thefr'esi stor 22-mey be conne ed ijhf shunt relation to "theinstrument 15 f0 purpose o'f s hnjn'tlng therurrentther' min are change.'ts reeding lWhentheffreque e r I impressed: across the t rzin'sfOr'merfrom the v-e' H for-arhi'ehfztlre' in calibrated,

Since the sonterfcon'dluctin eondenser terininil bnhing throu' h. tl'leireeistor 1 0 .-t0 the e2ls"ingjl of he e,

bushing will traverseiithei resieto H "average 'valueofthisftihgrggngcnr n u be determined by measu ing th the resisto1---1Q; everyf'altemat by "measuring the "average tim p fled currenfiwavejthfoughf e31 value of n g f more reportl 1 he; greet Tl t'B.IlC6.,b f- 11611011 gns'er er is nontn, the maxlrnuln or crest value ofthel voltage of the transformer 1 may be deter- 11m;

I mined by operating the contact-making and breaking device 16' andnoting the'reading of the amineter 15. Of ,course, it is understood thatthe ammeter is calibrated to indicate the maximum value of the voltagewave or the root-mean-square value of a sine wave having the samemaximum value. That is to sa the value marked on any part of the scaleis directly proportional to the current traversing the winding of theammeter 15 and inversely proportional to the capacitance ofthe'condenser. and'the frequency of the voltage to be measured.

Since the scale of the ammeter 15 may be calibrated to correspond'to anycapacitance or frequency, it is desirable to utilize the same scale whenthe frequenc changes, and, in order to permit the use o a single scale,irrespective of the frequency of the voltage to be measured, I rovidethe ad'ustable re ister 22 a selected portion of w ich 1 connect.iushunt. re ation .toflthe ammet r 15 f shunting current therefrom inaccordance with the change in frequency. That is to say, the movablecontact member 28 of the resistor 22 is'set at a point to correspond tothe reading of ,a frequencyyinete'r 11 that is connected to thesecondary winding 29 of the transformer 1. When the contact memher 28 isset in the correctposition, suflicient current will be shunted from theam-' meter 15 to cause it to indicate correctly.

Assuming that the amm'eter 15 is calibrat'ed to read oorrectly' vvhenthefrequency is s'i'x'tyc'ycles and my .device is not used, if

the frequency should increase to sixty-one cycles; theammeter 15 wouldread substantially 1.66 per cent. higher than its correctvalii'e'."However,' 'i fm device is used, and if theconta'ct member 28 is movedto a position corresponding-to sixty-one cycles, the amount ofresistance connected in shunt to will hevdecreasedto such an ex- IIantiajllyLfifipercent. less current will traverse the amm'eter to causeit to indicate-.zcorrectly.

Th resistor 10 may be omitted if it is desired to ermit all of the charing current of the condenser-to traverset e winding of the instrument15. v v

' Changes may be made in the-method of connecting the condenser,the'means for rectifying the current and themeans for shunting-thecurrent from the-'amm'eter without departing from the spmt and scope ofmy nvention as set forth inthe appended claims.

I claim-as my invention 1. .A device f r lndi o'atm the maximum valueonly of the; volta e 0- an electric circu'it comprising an in'icatinginstrument, meansfor supply ng an actuating force to imam the indicatinginstrument that is dependent in value upon the frequenc and the value ofthe voltage to be measure and means for neutralizing the eifect ofachange in frequency upon the indicating instrument.

2. A voltage-measuring device comprising a condenser adapted to besupplied with current proportional to the frequency and the voltage tobe measured, a measuring instrument for indicating the value of thecurrent traversin the condenser and means for ad-- justing t einstrument indicate voltage independently of changes in the frequency 3.A voltage-measuring device comprisin a condenser adapted to be suppliedwit current proportional to the frequency and the voltage to bemeasured, a measuring instrument for indicating the value of the currenttraversirig the condenser and a calibrated resistor any desiredportionof which may be connected in arallel relation to the instrumentfor adjusting it to indicate voltage independently of changes in thefreconnected across the circuit, indicating quemz. 35 4:. devlce forindicating the voltage of: an electric circuit comprising a condensermeans for determiningthe value of the chargln current ofth'e condenserand means e for so s unting current from the said indicating means thatit'will indicate the'voltage' independently of change in frequency ofthe.

circuit.

.-.A measuring device for an electric circult compris ng a condenserconnected across the circuit, means for indicating the 'charg ingcurrent of the condenser and means for so shunting current from the saidmeans thatjlts indications are independent of 'changes in the frequencyof the circuit.

cuitcoinprising a condenser connected across the circuit, means forindicating the charg- 1n current of the condenser and an ad ustab eres1stor for so shunting current from the:

"said means that its indications are independs ent of changes in thefrequency of the circuit.

I In. testimony whereo I have hereunto subscribed my name this 28th dayof Jan. 1916.

LEWIS W. CHUBB.

